In order to curb the rising prevalence of allergic diseases, there is an urgent need to identify etiologic factors that would generate novel preventive or therapeutic strategies. We have some understanding of the role of DNA sequence variation in susceptibility genes contributing to the risk of allergic diseases, however, DNA sequence variation alone does not account for all the observed heritability of allergy. In addition, the combined effects of genes and the environment are more strongly associated with allergy than genes alone. Both these observations suggest a role for epigenetic modifications, which constitute a transmissible memory of past exposures. In particular, environmental exposures in early life seem to have a strong influence on allergies. Indeed, there is scientific agreement that epigenetic studies commencing during pregnancy are needed. While we cannot change DNA sequence, there are acceptable means to prevent or alter epigenetic modifications by changing the environment. To provide critical information as to the role of epigenetic factors, specifically DNA methylation, in allergic disease we will conduct a multigenerational study in the Isle of Wight birth cohort (n = 1,456). This cohort of an F1 generation (now age 20 yr) and their parents (F0) is being expanded to include the next generation (F2) starting during their gestation. Asthma, eczema, rhinitis, and allergic sensitization were characterized in F1 at their birth, and at 1, 2, 4, 10 and 18 years. The F1 women are now of reproductive age, which facilitates the study of epigenetic modifications during F1 pregnancies and in their offspring (F2). We propose to conduct a four-step research study: (1) Filtering of CpG (cytosine-phosphate-guanine) sites based on association of their methylation status with atopy in F1 women; (2) Testing of selected CpG sites for vertical transmission and environmental impacts; (3) Biological validation of selected and tested CpG sites using gene expression arrays; and (4) Prediction of allergic sensitization and eczema in F2 infants. We will start with screening of 27,578 CpG sites located within proximal promoter regions of 14,495 genes and expect to focus on the methylation status of approximately 10-15 genes in prediction of allergy in F2 infants. We will test four hypotheses: (H1) Specific methylation is transferred from parent to child with a stronger vertical transmission of maternal methylation. (H2) DNA methylation in mothers (F1) and their children (F2) is related to modifiable environmental conditions during gestation. (H3) Methylation of selected CpG sites correlates with observed differences in gene expression. (H4) Selected methylation and gene expression patterns in the F2 generation are predictive of increased cord serum IgE level, eczema in infancy, and allergic sensitization. Our research team has a long track record of successful collaboration and two related projects are currently supported by NIH. The team comprises epidemiological and biostatistical knowledge at the University of South Carolina, epigenetic expertise at the University of Southampton (UoS), clinical partners at UoS and the David Hide Asthma & Allergy Research Centre on the Isle of Wight, and a genetics laboratory at Michigan State University.